1. FIELD OF THE INVENTION
The present invention relates to a system for filling granular material to hard capsules. More particularly, it is concerned with a method and an apparatus for filling bodies of medicinal hard capsules with a predetermined quantity of granular material such as granules or fine granules. The capsules are usually made of gelatin and mated in cap/body prelocked combination but are separated temporarily for the filling operation.
2. DESCRIPTION OF THE PRIOR ART
Roughly classified, there are three widely known systems for successively filling the conventional medicinal hard gelatin capsules with a predetermined quantity of medicinal substance or food material, depending on the physical properties of the material to be filled. The first of which is called as "Die Compression System" and is employed mainly for filling powdery medicine. The second one is "Gravitation System" which is applied to filling granular materials such as granules and fine granules. And the last one is "Pumping Unit System" employed for filling liquid.
Of these three systems, a capsule filling machine according to the "Gravitation System" is almost similar to that of the "Die Compression System" in its mechanical aspects. The application of the "Gravitation System" machine is however restricted to the granular material, such as, granules and fine granules which have excellent fluidity, and the machine is hardly applicable to the handling of the powdery material which has poor fluidity. The machine is generally composed of a metering chamber of a predetermined capacity provided on its metering disk. The granular material piled up on the upper surface of the disk is gravitated down into the chamber wherein the material is portioned. In the next step, the portioned material in the metering chamber is then allowed to fall down into the body of the hard gelatin capsule positioned under the outlet of the metering chamber with virtually no artificial force.
Even in the case of the granular material of excellent fluidity, the conventional "Gravitation System" machine is however still unsatisfactory, if an extremely high standard of accuracy and small variance in the quantity of the material actually filled in the capsule are imposed. Namely, so-called bridging of the material may sometimes be formed at an inlet of the metering chamber, in the metering chamber itself and at its outlet during the gravitational travel of the material from the upper surface of the metering disk down to the metering chamber and from the chamber into the body of the capsule to invite an inaccurate portioning or an irregular transposition of the material.
Therefore, in the conventional machine, all of the inlet of the metering chamber, the metering chamber itself and its outlet have heretofore been usually designed as widely as possible in order to prevent the bridging of the granular material to be filled.
The proposed wide design of the inlet of the metering chamber, the metering chamber itself and its outlet, however, means occupation of a large horizontal span by these components, and results in a limitation on the number of the components such as metering chambers for unit area of the capsule filling machine. This in turn reflects on an inconvenience of lowering of the filling (capsule handling) capacity for unit time, i.e., productivity of the machine.
Furthermore, in the conventional machine, the adjustment on the capacity of the metering chamber is usually performed by lateral insertion of a capacity-restricting means, for instance, a comb-teeth type device, into the metering chamber. Application of this type of adjustment is, however, restricted to a machine having metering chambers of just two rows at most. Therefore, the adjustment in a machine having the chambers in three or more rows must have been made by interchanging the metering disks of various thickness.